BACKGROUND:

Isolated systolic hypertension, defined as systolic blood pressure of 140 mm Hg or greater with a diastolic blood pressure below 90 mm Hg, is known to be associated with an increase of risk of coronary heart disease and stroke. The HANES I group estimated that isolated systolic hypertension, uncommon under 54 years of age, occurred in 5 percent to 10 percent of adults over 55 years and was less common than systolic-diastolic elevation. Evidence was not readily available that there was effective and safe therapy to correct isolated systolic hypertension. At that time, there was no body of clinical or research data that conclusively proved that such therapy, if available, was beneficial.

Several groups had expressed interest in a clinical trial on systolic hypertension in the elderly. Among these were the House Select Committee on Aging, a Blue-Ribbon Panel on Hypertension in the Elderly, Citizens for the Treatment of High Blood Pressure, panels and experts associated with the National High Blood Pressure Education Program, the National Institute on Aging, the National Institute of Mental Health, and the National Institute of Neurological and Communicative Disorders and Stroke.

A Policy and Data Monitoring Board was appointed to review the protocols for the pilot studies as they developed and make recommendations to the Director of NHLBI. The Policy and Data Monitoring Board reviewed the accumulated data on April 8, 1983 and recommended to the Institute that a full scale trial be implemented. The recommendation was accepted by the Director, NHLBI and was presented to the National Heart, Lung, and Blood Advisory Council at its meeting in May 1983. A full scale trial was conducted.

DESIGN NARRATIVE:

A randomized, double-blind design, with two groups and fixed sample size. The 551 participants were randomized in a stratified double-blind manner to either chlorthalidone or matching placebo in a ratio of 4:l. Subjects failing to reach goal blood pressure were randomized a second time to receive one of the following drugs in addition to chlorthalidone: reserpine, hydralazine, and metoprolol. Subjects on placebo in Step I who did not achieve goal had a corresponding Step II placebo added to their regimen.

Men and women, aged 60 or over. Isolated systolic hypertension. Normal diastolic pressure of less than 90 mm Hg.